# ---
# title: 617. Merge Two Binary Trees
# id: problem617
# author: Tian Jun
# date: 2020-10-31
# difficulty: Easy
# categories: Tree
# link: <https://leetcode.com/problems/merge-two-binary-trees/description/>
# hidden: true
# ---
# 
# Given two binary trees and imagine that when you put one of them to cover the
# other, some nodes of the two trees are overlapped while the others are not.
# 
# You need to merge them into a new binary tree. The merge rule is that if two
# nodes overlap, then sum node values up as the new value of the merged node.
# Otherwise, the NOT null node will be used as the node of new tree.
# 
# **Example 1:**
# 
#     
#     
#     Input: 
#     	Tree 1                     Tree 2                  
#               1                         2                             
#              / \                       / \                            
#             3   2                     1   3                        
#            /                           \   \                      
#           5                             4   7                  
#     Output: 
#     Merged tree:
#     	     3
#     	    / \
#     	   4   5
#     	  / \   \ 
#     	 5   4   7
#     
# 
# 
# 
# **Note:** The merging process must start from the root nodes of both trees.
# 
# 
## @lc code=start
using LeetCode

## add your code here:
## @lc code=end
